Chapter 1. Introduction
13
1.4 E1 Signal Structure
E1
link
line
rate
The
E1
line
operates
at
a
nominal
rate
of
2.048Mb/s.
E1
link
line
coding
The
basic
E1
line
signal
is
coded
using
either
the
Alternate
Mark
Inversion
(AMI)
or
HDB3
rule.
In
the
AMI
format,
"ones"
are
alternately
transmitted
as
positive
and
negative
pulses,
whereas
"zeros"
are
transmitted
as
a
zero
voltage
level.
AMI
is
not
used
in
most
2.048Mb/s
transmissions
because
synchronization
loss
occurs
during
long
strings
of
data
zeros.
In
the
HDB3
format,
a
string
of
four
consecutive
zeros
is
replaced
with
a
substitute
string
of
pulses
containing
an
intentional
bipolar
violation.
The
HDB3
code
substitutions
provide
high
pulse
density
so
that
the
receiving
equipment
is
able
to
maintain
synchronization
with
the
received
signal.
The
8/16-CHANNEL E1
supports
two
E1
line
codes:
AMI
coding.
HDB3
coding.
The
8/16-CHANNEL E1
supports
only
transparent
unframed
format.
ie.,
The
E1
will
pass
through
with
its
original
framing
structure
completely
intact.
1.5 T1(DS1) Signal Structure
T1
link
line
rate
The
T1
line
operates
at
a
nominal
rate
of
1.544Mb/s.
T1
link
line
coding
The
basic
T1
line
signal
is
coded
using
either
the
Alternate
Mark
Inversion
(AMI)
or
B8ZS
rule.
In
the
AMI
format,
"ones"
are
alternately
transmitted
as
positive
and
negative
pulses,
whereas
"zeros"
are
transmitted
as
a
zero
voltage
level.
AMI
is
not
used
in
most
1.544Mb/s
transmissions
because
synchronization
loss
occurs
during
long
strings
of
data
zeros.
In
the
B8ZS
format,
a
string
of
eight
consecutive
zeros
is
replaced
with
a
substitute
string
of
pulses
containing
an
intentional
bipolar
violation.
The
B8ZS
code
substitutions
provide
high
pulse
density
so
that
the
receiving
equipment
is
able
to
maintain
synchronization
with
the
received
signal.
The
8/16-CHANNEL T1
supports
two
T1
line
codes:
AMI
coding.
B8ZS
coding.
The
8/16-CHANNEL T1
supports
only
transparent
unframed
format.
ie.,
The
T1
will
pass
through
with
its
original
framing
structure
completely
intact.
Summary of Contents for FMUX160
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